A Guide to the Geology of Rocky Mountain National Park, Colorado
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0.0Thompson River Entrance, Rocky Mountain National Lark. Just beyond the entrance the road to Bear Lake turns abruptly left, crossing Thompson River to Camp Woods in Tuxedo Park. Keep straight ahead on road to Moraine Park. The gravel and boulders on the right belong to the moraine of a glacier older than the last or Wisconsin stage of glaciation. This glacier flowed down the Thompson Valley and spread its deposits beyond the limits of the later glacier (see p. 19, point 2.4 miles).

0.1Steep grade around the base of Eagle Cliff. Dark schist with intrusions of white pegmatitic granite (granite containing large crystals) is exposed in road cut on right. Note the shining crystals of black mica in the schist which lie in parallel planes and cause the rock to cleave readily in those planes. The granite has been intruded in thin layers along the cleavage planes of the schist and in places has broken across them. At bend in road is exposed a mass of granite which has welled up into the schist and is disintegrating due to the breaking down by weathering of the feldspar crystals which are present in it. Just beyond, a lense of pink and white granite from 2 to 6 feet thick has been intruded between the planes of the schist and dips to the east. Its color is due to the presence of both pink and white feldspar crystals.

0.3Crest of terminal moraine of the great glacier which during the Wisconsin or last stage of the Ice Age covered Moraine Park.

0.5Road follows base of terminal moraine which is banked against the foot of Eagle Cliff. Here the advance of the ice was halted by the cliff, and the gravel and sand carried by the glacier were deposited in a ridge as the ice melted.

0.7Junction with road to Stead's Ranch. Keep right. To the south rises the pine-covered south lateral moraine of the former Thompson Glacier. Its height indicates the height of the glacial ice which decreased toward the east as the ice melted in the warmth of the lower altitude. At the end of the former glacier the lateral merges with the terminal moraine.

To the north, beyond the groves of aspen, stretches the pine-covered north lateral moraine, its western end banked against the mountain at the mouth of the canyon down which the ice flowed. The top of this moraine, like that of the south lateral, slopes to the east, the inclined line of its crest being plainly visible against the mountain side.

The flat valley of Moraine Park (fig. 12) was the melting basin of the glacier and was occupied as the ice melted back by a glacial lake. The waters of this lake, impounded by the terminal moraine, were later drained away when the outlet cut through this natural dam. The present stream swings in broad meanders across the flat which was the lake bed, because it does not have enough fall to give direction to its waters. Rising from the flat in the distance is a rock island which the glacier was unable to destroy, although it ground down the west side to a gentle slope.

Figure 12.—Moraine Park from the museum. The even-topped pine-covered ridge on the left is the south lateral moraine, or deposit of boulders, gravel, and sand, left by the former Thompson Glacier. Its height indicates the height of the glacial ice. The flat is the bed of a former lake, impounded as the glacier melted, by the terminal moraine which the glacier threw across the valley. Note the U-shaped gorge, in distance on right, down which the glacier moved. Photograph by Carroll H. Wegemann

Around the east side of the lake the road follows what appears to be an old lake terrace or shore line formed by the waves when the lake stood at its initial high stage before the lowering of its outlet. As the outlet was deepened and the waters drained away, the lake established a new and lower shore line leaving the old terrace dry, to be cut away, in part, by the waves and stream erosion.

1.1Moraine Park Museum, on right, contains exhibits illustrative of Indian life, pioneer history, wildlife, and glacial geology.

1.4Begin climb of north lateral moraine (Wisconsin stage or last glacial advance) of Thompson Glacier. The open air amphitheatre is on the south side of the road.

1.9Road curve on crest of moraine.

2.1North base of lateral moraine (Wisconsin stage).

2.3Cross Beaver Brook.

2.4Road emerges from aspen grove in Beaver Park. Ahead are scattered pine trees growing on a low gravel and boulder ridge which is the north lateral moraine of an earlier glacier than that of the Wisconsin stage, the moraine of which has just been crossed. The older glacier was larger than its successor. It flowed down the Thompson Valley and occupied Moraine Park, but all evidence of it has been obliterated by the later glaciation except in Beaver Park and Tuxedo Park, where its moraines lie outside the area covered by the later ice. The gravel in these old moraines is very much weathered. In fact some of the stones can be crumbled in the fingers. The gravel has obviously been subjected to weathering for a period several times as long as that to which the practically unweathered gravel in the moraines of the last ice advance was subjected. The old lateral moraine can be traced for a short distance down the valley until it merges with the old terminal moraine which turns south and is banked against Eagle Cliff. The road follows the south side of the old moraine to the west.

2.7Curve to the right across the old moraine which is so low at this point as to be scarcely recognizable.

2.8Dirt road leads left to Upper Beaver Park. Keep to the main road.

3.1Sharp curve to left on shoulder of Deer Mountain. From this point an excellent view can be had of the several moraines just described.

3.3Rock cut. A light-colored granitic dike containing large crystals of shiny mica, which separate in thin sheets, is well exposed on left and can be seen also on right. The dike represents molten rock which was intruded into the older rock at great depth and cooled so slowly that the large crystals had time to form before the molten rock solidified. Erosion has lowered the surface and exposed the granite.

4.6Second rock cut is through rusty colored granite which here stands in a ridge because it is harder than the rock on either side. From this point one may view the even-crested north and south moraines of the last Thompson Glacier. Longs Peak is the highest flat-topped summit dominating the skyline on the south.



5.3Deer Ridge Junction. The left road is the usual route taken to Fall River Pass via Trail Ridge. The right road leads to the same pass by way of Horseshoe Park and Fall River. It is a narrow winding mountain road, but is safe for experienced mountain drivers. Beyond Chasm Falls it is open only to cars going up. By taking it one can make a circle trip, returning down Trail Ridge to Deer Ridge Junction. For this circle trip over the Fall River Road keep right. If you decide to take the Trail Ridge Road, keep left, and turn to page 29, point 5.3 miles using the left-hand mileage column and reading the descriptions of the various points in reverse order. In other words, read up on the pages.

5.9In the road cut on left large glacial boulders are seen resting on poorly exposed bedrock which originally formed the south side of the Fall River Valley. When the glacial ice moved down this valley it deposited its lateral moraine against the bedrock and the road cut has exposed the basal boulders. Some of these have been moved to protect the bank against erosion, but their position still marks the base of the moraine. Just beyond, the road crosses Hidden Valley Creek, the origin of which will be described from Rainbow Curve (see p. 27, point 9.3 miles) on the Trail Ridge Road.

6.8Base of lateral moraine on south side of Horseshoe Park. The flat valley, like that of Moraine Park, is the bed of a glacial lake impounded by a terminal moraine which crosses the valley 2 miles farther down. This stop is on an old lake terrace built by the waves when the lake stood at one of its higher stages.

6.9Edge of terrace, against which the waves broke after the lake level had been lowered by the deepening of the outlet through the terminal moraine.

7.1Cross Fall River. Just ahead the road forks. Take left road up valley, leaving Route 34.

7.5Fall River Lodge.

7.8Roaring River. The rapid fall of such side streams is due to lowering of the Fall River valley by the last glacier. This left the mouths of the side valleys, which contained smaller glaciers or no glaciers at all, "hanging" so that their waters now reach the main valley by a series of cascades. It is evident that the valley of Fall River must have been lowered some 400 feet by the gouging of the glacial ice.

8.5Point of granite on right projects into valley. Below this point the road follows the foot of the north lateral moraine of the Fall River Glacier. In the narrow valley above, however, there is no moraine because the ice was so confined and flowed under such pressure between the granite walls that no gravel was dropped along the base of the cliffs. Nevertheless, some morainal material was banked high up on the valley sides.

9.0Road to Endovalley Campground. Keep right.

9.4Chiquita Creek. Before the last glacier had deepened the valley of Fall River and thrown its lateral moraines across the mouths of its side streams, Chiquita Creek joined the main valley without a fall like any normal stream. Now, due to the work of the glaciers of the Ice Age, it cascades down to the main valley in a series of falls. The rock is coarse reddish granite.

9.6The granite ledge just above the road has been smoothed and polished by the stones frozen in the base of the glacial ice and ground across it by the glacier's flow.

9.7Pot hole on right next to road. This circular hole 2 or 3 feet in diameter was drilled by stones revolving in a whirlpool in some side stream which probably flowed at this level during, or just after, the last glaciation. Note that the main stream is several hundred feet below.

10.0First switch-back.

10.2Glacial polish on ledge just above road similar to that at 9.6 miles.

10.4Chasm Falls. The beautiful waterfall is about 25 feet in height and is drilling, at its foot, a pot hole similar to that at point 9.7 miles. From this the water drops about 5 feet into a second hole, the half-round side of which may be seen in the cliff above the water. About 20 feet downstream from the base of the main fall the remains of a third pot hole are to be seen. It is evident that the stream is literally drilling out its narrow gorge in the solid rock by revolving loose boulders in its whirlpools. As the cataract recedes, the upstream side of the last pot hole is cut away so that the half-round hollows in the walls of the gorge are all that remain.

There is glacial polish on the rock ledge just above the parking area.

10.7Here a perpendicular face of granite, some 20 feet long and 12 feet high, rises above the road. Its top is rounded and polished by the gravel and sand frozen in the ice of the former glacier. The rock was jointed or cracked during the uplift of the mountains and, after the polishing of the upper surface, large blocks were broken off along joint planes and carried away by the moving ice, leaving the smooth face of the joint exposed. This was later polished by the ice.

11.0Glacial polish is visible about 150 feet above the road showing the height of the former glacier.

11.8In line with the road is Mount Chapin. The banding of the old dark schist and the lighter granite, which as molten rock was intruded into the schist when both lay deep within the earth, is plainly seen. Mountain uplift and erosion have brought the rocks to the surface and erosion working along joint planes has carved the peculiar spires and pinnacles.

11.9Granite broken into blocks by joints. These were produced by the pressures and strains under which the rocks were placed during the mountain uplift.

14.0Surface of schist and intrusive granite beside the road. These rocks have been ground smooth by the glaciers for they formed the floor of the old glacial valley. The present stream flows in a gorge which it has cut since glacial time, leaving part of the old valley floor as a bench along which the road has been built.

The schist and granite were at one time so deeply buried within the earth that the pressure upon them from all sides exceeded the crushing strength of the rock. Under such conditions no crevasses could form and during earth movement the rocks bent and flowed like thick tar. Note that much of the bending took place after the intrusion of the light granite. At one point a band of granite has been folded and the fold, by continued lateral pressure, has been overturned, broken, and one side thrust over the other. This type of thrust-folding and faulting is characteristic of the mountain building which took place at the end of the Mesozoic era when the Rockies were first formed. It often happens that a single rock may show in miniature a type of folding which is characteristic of an entire mountain range.

14.2Canyoncito (fig. 13). This little canyon has been cut by the stream in the valley floor since the retreat of the last glacier. Note that glacial grinding is evident on the terrace over which the road runs, but that there is none in the little canyon. If we assume that the glacial ice began to melt back from the valley below Horseshoe Park some 25,000 years ago and retreated steadily to the cirques of Fall River Pass, then it may have left this part of the valley some 10,000 years ago. If this reasoning is correct, it has required about 10,000 years for the stream to cut Canyoncito.

Figure 13.—Canyoncito from Fall River Road. There is glacial polishing on the surface of the rocks to the right, but the rugged gorge shows no sign of glacial action. It is evident that the gorge has been cut in the 10,000 years since the ice melted from this part of the valley. Photograph by Carroll H. Wegemann

15.2Willow Park. This meadow was the bed of a small lake impounded by a terminal moraine which marked a pause in the retreat of the glacial ice. Such a moraine is known as a recessional moraine.

In the next mile are numerous intrusions of coarse-grained granitic rock known as pegmatite. The molten rock, deep within the earth from which these intrusions solidified, probably contained, under great pressure, much steam which made it thinly fluid. It cooled slowly deep below the surface, giving the large crystals time to grow.

17.0Large mass of pegmatitic granite several hundred feet wide which has been intruded into the schist.

From this point an excellent view is to be had of three cirques or basins in which glacial snow and ice accumulated at the head of Fall River. From these the great glacier flowed down the valley.

NOTE.—Left hand column of figures below is for the use of travelers coming up from Poudre Lakes.)

4.518.4Parking area at store and museum on Fall River Pass. The cirques previously mentioned lie to the south, and beyond them the ridge is capped by the remnants of an old lava flow which is better exposed at Iceberg Lake (see p. 25, point 2.0 miles).


There is not time on this circle trip to drive to Grand Lake, but if you have an hour to spare turn right on the road to Grand Lake, and use the right hand column of figures in log. Drive down as far as Poudre Lakes on the Continental Divide. If you do not care to take this trip but wish to go east down Trail Ridge Road, turn to page 24, point 0.0 miles in right-hand column.

4.018.9Overlook. Specimen Mountain, 3 miles to the west across Cache la Poudre River, appears to be an extinct volcano and the probable source of the lava previously mentioned. The mountain is situated on the Continental Divide 2 miles north of Poudre Lakes and can be reached by a trail from the Lakes. Erosion has long since destroyed the old crater, which stood above the highest point of the present mountain.

Figure 14.—Volcanic Rocks of Specimen Mountain, and the Never Summer Range, Specimen Mountain is an extinct volcano, its sides, as shown in the foreground, formed by black pitchstone or volcanic glass, white volcanic ash, fragments of rock blown out by the explosions, and mud flows. The ancient crater has been destroyed by erosion. Photograph by Carroll H. Wegemann

That the mountain was a volcano may be inferred from the nature of the rocks which are exposed on its top and sides. Like many volcanic cones, the mountain is built up of alternating layers of black volcanic glass (pitchstone), lava, white volcanic ash, mud flows, breccia, and pumice (fig. 14). Notes on the formation of these rocks follow:

Volcanic glass is produced when molten rock flowing out upon the surface is chilled so quickly that mineral crystals do not have time to form in it.

Ordinary lava is cooled more slowly, but not slowly enough for the rock to become completely crystalline like granite, which is cooled very slowly far below the surface.

Volcanic ash is rock dust blown out by the terrific explosions of the eruption.

Mud flows are formed when this dust is washed out of the atmosphere by the torrential rains which frequently accompany the eruption, the rains being due to the condensation of clouds of steam emitted from the volcano.

Breccia is formed of fragments of the sides of the crater, blown out during the explosions.

Pumice is lava charged with gas, the bubbles of which expand when the pressure upon the lava is reduced as it reaches the surface. The resulting small cavities when filled with air cause the pumice to float on water.

All these rocks are to be seen on Specimen Mountain, mute reminders of a time, in the distant past, when volcanoes were active in this region.

The mountain was probably named for the opal, agate, and delicate crystals of topaz which are found lining some of the small cavities in the volcanic deposits.

1.221.7Exposed on the south side of the road, about 400 feet beyond the end of the retaining wall, is greenish gray soft rock which represents an old mud flow from the volcano. At higher and lower levels along the road are the ancient rocks of the pre-Cambrian era, and it is evident that the valley of the Cache La Poudre and the lava flow at Iceberg Lake present interesting relationships. Assuming that lava flowed from Specimen Mountain to Iceberg Lake, it could not have done so had the valley of the Cache La Poudre been present at the time of the flow. It is possible that the lava at Iceberg Lake flowed from a vent other than that of Specimen Mountain, but there is no evidence of such a vent. A possible explanation is that the volcanic deposits from Specimen Mountain completely filled an old valley which had been cut in pre-Cambrian rocks at the location of the present valley of the Cache La Poudre; that, in one of the last eruptions of the volcano, lava flowed across this fill to what is now Iceberg Lake; and that subsequent erosion excavated the present valley in the filling of the former valley, exposing some of the old mud flows which were part of the filling and the much more ancient rocks which formed the south side of the old valley. The mud flows, therefore, are merely a veneer partly covering the more ancient rocks.
0.022.9Parking area at Poudre Lakes. These lakes are on the Continental Divide although in a valley much lower in elevation than Fall River Pass. A glance at the park map will show that because of peculiarities of stream development the highest mountain peaks are not always along the Continental Divide.

(NOTE.—If you have entered the park from the west, set your speedometer at 0.0 at the parking area at Poudre Lakes and read paragraphs in reverse order up to 4.5 in the left-hand column of figures. At Fall River Pass reset at 0.0 and continue as below.)

Returning to Fall River Pass, reset the speedometer at 0.0 and use the right-hand column of figures. The left-hand column is for the use of those driving in the opposite direction.


22.90.0Road junction just southwest of museum and store at Fall River Pass. If you are traveling east, keep right on Trail Ridge Road.
21.91.0Overlook on curve. To the west, across the head of the valley of the Colorado River, rise the Never Summer Mountains, 7 miles away. This overlook is at 12,000-feet elevation on the Upper Flattop peneplain, an old erosion surface formed not far above sea level and raised to its present elevation during the last uplift of the region. Directly to the south, across Forest Canyon, rises the cone of Mount Julian, the next prominent point to the west being Mount Ida, the long northwest slope of which merges with the Upper Flattop surface. Across the canyon and extending to its very rim is a bench about 500 feet below the Upper Flattop surface, the origin of which was described in detail on page 10. It represents the beginning of a lower erosion surface which was cut by the stream after the initial uplift of about 500 feet had taken place. Its presence records a considerable pause in the uplift of the land before further elevation finally brought the mountains to their present height.
20.92.0Iceberg Lake. The rock which forms the wall of the cliff back of the lake is red dish brown and differs in appearance from the old pre-Cambrian rocks seen at other points on the road. It is the same lava flow which was observed south of Fall River Pass.

Looking north along the ridge, which is a continuation of the cliff, it will be noted that there is pre-Cambrian rock next to the lava and that it forms the north end of the ridge, being rather poorly exposed in, and below, the north point on the skyline. Across the highway, just south of Iceberg Lake, pre-Cambrian rock is also exposed. The pre-Cambrian. therefore, borders the lava on both sides. It is evident that the molten lava which solidified to form the rock of the cliff must have flowed down a valley cut in the older rock.

Southeast from Iceberg Lake there is an excellent view of the Upper Flattop peneplain (fig. 4). When it was formed it was not quite a plain, for above it rose a line of low rounded mountains, the remnants of the first Rockies. The Mummy Range to the northwest was part of the line. The northwest side of this range shows the old erosion surface merging with the mountain slope. This surface is, however, being rapidly destroyed by the streams which are cutting canyons into it from the east. Farther to the south the group of mountains—Ida, Julian, and Terra Tomah—appear to have been one rounded mountain rising above the plain before the erosion of water and ice cut the canyon of the Gorge Lakes into its heart. Stones Peak may have been part of the same mass before it was separated from it by the cutting of the gorge of Hayden Creek, the next gorge to the east.

On Trail Ridge, about half a mile to the southeast, where the road follows the narrowest part of the ridge, the slopes on either side look as if they were roughly terraced. The soil is but a few feet thick and rests on a sloping surface of bedrock. In the spring when the snow melts, or during heavy rains, the soil becomes saturated with water which not only increases its weight but makes it slippery. Masses of soil, bound together by plant roots, tend to slide gradually for a few inches, or a few feet, down the slope, breaking away from the turf above and overlapping the turf below, thus producing the terraces.

18.64.3Rock Cut, 12,110 feet elevation. To the southeast is the gorge of Hayden Creek. Directly south across Forest Canyon the view is up the canyon of the Gorge Lakes. There are six of these lakes in the canyon proper. One, at an elevation of 12,400 feet, is the highest lake in the park. It occupies an old glacial cirque, the cliffs of which shelter it from the sun's rays so that it is never free of ice. The gorge itself was originally cut by streams but has been entirely reshaped by the ice of former glaciers. It contains numerous cirques. Its rugged outlines are in marked contrast to the old erosion surface which, as already mentioned, forms the summits of the surrounding mountains. Nor is it difficult to reconstruct in imagination the shape of the rounded mountain mass before erosion gashed it with cirques and canyons. The landscape of the old plain with its low mountains must have been monotonous. The spectacular scenery of today is due to the comparatively recent uplift of this region and to stream and ice erosion.
15.67.3Road crosses to Hanging Valley on north side of Trail Ridge. There are three stone cabins north of road. To the south, across Forest Canyon, is a view of Hayden Creek with several abandoned glacial cirques, the collecting basins of former glaciers, near its head. West of its mouth a great cirque has been cut into the side of Terra Tomah, partly destroying the old erosion surface which forms the top of this mountain.
14.98.0The bark on the spruce, fir, and pine trees at timber line where exposed to the wind-driven snows of winter and the sand blasts of dry weather is worn off the windward side.
14.08.9Guard wall. To the west is Sundance Mountain with a remarkably fine example of a glacial cirque cut into its eastern flank (fig. 11). To the north across Fall River Valley the switchbacks on the Fall River Road are visible.
13.69.3Rainbow Curve affords a magnificent panorama. To the north lies the Mummy Range. Its peaks, northeastward from Fall River Valley, are: Mount Chapin, Mount Chiquita, Ypsilon Mountain, Fairchild Mountain, and Hagues Peak, with Mummy Mountain southeast of Hagues. Note on Ypsilon Mountain the banding of the dark schist and the white granite which, as molten rock, was intruded into it when both lay deep within the earth.

Below lies Horseshoe Park in the broad valley of Fall River. Beyond the tree less meadow in the distance, which is a former lake bed, a low wooded ridge crosses the valley (fig. 15, C—4). This is one of the terminal moraines of the Fall River Glacier (Wisconsin stage). It was this natural dam which impounded the lake waters and through which the outlet finally cut its channel, draining the lake and leaving several small ponds in the irregularities of its bed.

Figure 15.—Horseshoe Park from Rainbow Curve, Trail Ridge Road. A—1, Big-Horn Mountain; A—4, crest of north lateral moraine of former Fall River Glacier, slopes east; B—2, The Needles, part of an old erosional surface at 10,000 feet elevation; B—6, bed of former lake impounded by terminal moraine; C—3; McGregor Mountain; C—5, terminal moraine of Fall River Glacier; C—7; south lateral moraine which merges at east end with terminal moraine; D—3 Castle Mountain, part of old erosional surface at 8,700 feet elevation; D—7, beaver pond in Hidden Valley; E—2, flat top of Deer Mountain, part of same erosional surface as that of The Needles. Photograph by Carroll H. Wegemann

On either side of the meadow rise the abrupt gravel slopes of the lateral moraines, 800 feet in height, the tops of which indicate the height of the ice in the valley (fig. 15, A—4). They slope eastward to the point where they merge with the crest of the terminal moraine (see p. 29, point 8.2 miles).

From the north end of the terminal moraine the north lateral moraine can be traced to the point where it crosses the valley of Roaring River. This valley also was occupied by a glacier, but one which apparently lacked the cutting power of the longer and straighter Fall River Glacier, It was unable to lower the bed of its valley as rapidly as did the glacier of Fall River, and the mouth of the side stream was left hanging 400 feet above the bed of the major stream to which it falls by a series of cascades, It is probable that the glacier of Fall River continued its flow longer than its smaller tributary, for it seems to have thrown its north lateral moraine across the Roaring River Valley. After the glaciers disappeared the stream was able to cut away part of this obstruction.

Note that almost no morainal gravel or sand was deposited on the point of Bighorn Mountain which projects into the valley and which felt the full force of the ice movement. The ice did drop its load, where it was moving with less power, in the more sheltered parts of the valley both above and below this point.

Turning now to the south lateral moraine (fig. 15, C—7), it is evident that this also threw a dam across the mouths of the side valleys coming in from the south. These valleys did not carry glaciers. Their waters were impounded by the moraine, back of which the road now runs, and were forced to flow eastward south of the moraine. The moraine is lower in this direction and the stream, which is called Hidden Valley Creek, at length reached a point where its waters could overflow the barrier and cascade down the moraine to the floor of the main valley. This little stream is crossed on the road from Deer Ridge Junction to Horseshoe Park. The beaver have built several dams across the stream back of the moraine, their ponds (fig. 15, D—7) being plainly visible from this point.

The flat-topped mountain in line with the road is Deer Mountain, along the base of which the road from Deer Ridge Junction to Beaver Park is located. Its top and the top of The Needles are parts of an old erosion surface similar in origin to the Flattop peneplain, but formed somewhat later. A remnant of a still lower plain of erosion is to be seen on the top of Castle Mountain, beyond and just to the left of Deer Mountain. As explained on page 10, these old erosion surfaces were formed, when the region stood at lower altitudes, by stream which had reached their limit of down cutting and were widening their valleys. These erosion surfaces have been for the most part destroyed by the streams which produced them, after further uplift gave the streams more fall and enabled them once more to deepen their valleys.

12.710.2Sign 2 miles above sea level.
10.712.2A dike several feet wide of dark rock known as dolerite has been intruded into the lighter granites and is well exposed at the side of the road. The same dike is believed to have been encountered in the Colorado-Big Thompson Diversion Tunnel which passes under the Front Range. The molten rock that formed the dike was forced into a fissure which apparently extended in a straight line for several miles. What appears to be the same dike can be seen on the south side of Mount Chapin.
9.313.6Many Parks Curve. The description of the Fall River Valley as given from Rainbow Curve (see p. 26, point 9.3 miles) applies equally well here. Note the excellent view of Longs Peak to the southeast and of Moraine Park shut in on north and south by the great timbered ridges of its lateral moraines. At the eastern end of Moraine Park rises Eagle Cliff. From the flat floor of the park rises the little granite island which is noted from point 0.7 miles. (See p. 18.) The treeless area to the north of Moraine Park is Beaver Park, bordered on its north side near the lower end by a narrow tree-covered ridge. This ridge is the lateral moraine of an older glacier which once flowed down the Thompson Valley. (See description at point 2.4 miles, p. 19.) This lateral moraine can be traced farther west by the thin line of trees which divides Upper Beaver Park.
7.815.1Curve into Hidden Valley. To the north lies the south lateral moraine of the Fall River Glacier which has dammed Hidden Valley and forced its waters to flow east as Hidden Valley Creek along the sooth side of the moraine. The road also follows the moraine.
7.615.3Beaver dams.
6.816.1Cross Hidden Valley Creek. The gravel and sand of which the moraine is built are exposed in the road cut on the left.
6.016.9Hidden Valley Creek has cut through a low point in the moraine on the left and drops by a series of cascades (not visible from this road but noted at point 5.9 miles (page 20) some 400 feet to the bed of Horseshoe Park.
5.317.6Deer Ridge Junction. This completes the circle trip. You may return to Estes Park by the paved road to the right or by Route 34 to the left. If the latter route is taken, set the speedometer at 5.3 miles.



5.3Deer Ridge Junction. Take road to left (north). For details of the log between this point and point 7.1 miles below see page 20.

7.1Junction in Horseshoe Park with road to Fall River Pass. Keep right on Route 34.

7.3Sheep Lake, a shallow pond in a depression in the floor of the ancient lake. Just beyond, the road climbs to one of the old lake terraces described at point 6.8 miles, page 20. There is another terrace 25 feet higher. These terraces are old shore lines formed when the former lake stood at high levels.

8.2Terminal moraine (Wisconsin stage) which impounded the ancient lake until the outlet cut its channel through it, draining the lake waters.

8.4Studio of David Stirling.

8.8East base of terminal moraine.

8.9Road follows, and cuts into, a north lateral moraine of what appears to be a glacier older than the Wisconsin, and which extended some distance farther down the valley than did the Wisconsin ice.

9.2Fall River Entrance to Rocky Mountain National Park.

9.3Side road to Bryson Cottages crosses the valley on recessional moraine.

9.5Small meadow, probably the bed of a former lake, lies between two recessional moraines which here cross the valley. McGregor Mountain on north shows, in its bare dome-shaped crest, the typical weathering of granite, the surface of which spalls off in convex slabs.

9.8Fish hatchery and bridge.

11.0Approximate end of glaciation. Below, the valley narrows abruptly and is apparently unglaciated.

13.9Estes Park.

Figure 16.—West side of Longs Peak with Glacier Gorge below. Photograph by Carroll H. Wegemann


A short but interesting drive is that to Bear Lake. Set your speedometer at 0.0 miles.


0.0Thompson River Entrance to the park. Take left hand road inside entrance and cross Thompson River to Camp Woods.

0.4Tuxedo Park. Road follows the outside base of the south lateral moraine of the Thompson Glacier (Wisconsin stage). South of this moraine the surface of Tuxedo Park is covered by very old morainal deposits of a glacier much older than the Wisconsin as shown by the disintegrated condition of the morainal gravel. This glacier was wider than was the Wisconsin Glacier and its deposits, therefore extend beyond those of the Wisconsin ice.

0.5In repairing a washout on the north side of the road at this point in 1935, human bones believed to be those of a woman were found several feet below the surface. They are said to have been scattered and mixed with charcoal and rested on a bed of white sand which may have been glacial outwash. The body was apparently cremated on the surface of the outwash from the glacier and the remains later covered by material washed down from the morainal ridge to the north. The information is insufficient to warrant positive conclusions, but the bones were probably very old. The skull is preserved in the Moraine Park Museum.

1.5Across the stream flat to the left is the terminal moraine of the former Bartholf Glacier which flowed down the valley of Glacier Creek.

1.7Stream cuts through this moraine.

2.0Fork. Keep left, crossing Mill Creek, and climb the east slope of the terminal moraine of Bartholf Glacier.

2.5Crest of moraine.

2.9West base of terminal moraine. Road follows the south side of the north lateral moraine of the Bartholf Glacier.

3.3Fork. Take left road to Glacier Basin Campground, a broad treeless flat which was the melting basin of the Bartholf Glacier. From this flat there is a commanding view of the Continental Divide and of the high, even-topped ridge formed by the north lateral moraine of the Bartholf Glacier.

The ridge ends on the west against the side of Flattop Mountain for which the Upper Flattop peneplain has been named. From this observation point it is difficult to appreciate fully the flatness of the mountain's top.

The first sharp peak on the skyline to the left of Flattop Mountain is Hallett Peak and in the cirque to the right of it lies Tyndall Glacier.

Left, or south of Hallett Peak, is Otis Peak, and just left and back of the latter, but hidden from view in the gorge, lies Andrews Glacier.

Note that the smooth side of Otis Peak slopes to the north and that a similar surface on Hallett Peak slopes to the south. These smooth surfaces appear to be the sides of one of the old erosion valleys cut in the Flattop peneplain after the initial uplift of that surface when the bench was formed at the head of Forest Canyon (see point 1.0 mile, p. 24). A similar surface appears on Thatchtop Mountain which is the second peak south of Otis and is nearer this point. To the right of Thatchtop and farther away is Taylor Peak and between them is the glacial valley of Loch Vale, U-shaped in cross section, containing a series of glacial lakes and Taylor Glacier hidden from view at its head.

East of Thatchtop Mountain lies Glacier Gorge, and east of that is Half Mountain against which rests the west end of the south lateral moraine of the Bartholf Glacier which rims Glacier Basin on the south. Beyond the long even crest of the moraine rises in majestic grandeur the flat summit of Longs Peak, 14,255 feet in elevation. Its perpendicular cliffs are the walls of ancient cirques.

Returning from Glacier Basin Campground to the main road, reset the speedometer at 3.3 miles. Turning left (west), continue the log. On the right rises the long ridge of the north lateral moraine of the Bartholf Glacier.

3.6Road cuts across a jutting point of this moraine.

4.0Road to Sprague's Lodge. Keep straight ahead.

5.1Trail to Bierstadt Lake which is on top of the great accumulation of moraine lying north of the Bartholf Glacier.

6.1Prospect Canyon. The old tunnel, driven in a futile search for minerals, is at the edge of an intrusive dike, here poorly exposed. Prospect Canyon is a small but abrupt gorge cut by the stream since the retreat of the glaciers from the valley.

6.9Glacier Gorge parking area, from which road climbs moraine.

7.2View of head of Glacier Basin Valley, its surface strewn with the deposits of former glaciers. These deposits have been trenched by recent streams since the retreat of the ice.

7.7Parking area at Bear Lake, This beautiful body of water occupies a depression between the rock cliffs which rise on its west side and the moraines of various ice advances on the north and east and south. It lies in the line of flow of the former Tyndall Glacier.

This is the end of the road and you must return down the valley by the same road up which you came.

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Last Updated: 11-Dec-2006